Pizgrischite, (Cu,Fe)Cu14PbBi17S35, a new sulfosalt from the Swiss Alps: Description, crystal structure and occurrence

Pizgrischite, (Cu,Fe)Cu14PbBi17S35, is a new mineral species named after the type locality, Piz Grisch Mountain, Val Ferrera, Graubunden, Switzerland. This sulfosalt occurs as thin, striated, metallic lead-grey blades measuring up to I cm in length, embedded in quartz and associated with tetrahedrite, chalcopyrite, pyrite, sphalerite, emplectite and derivatives of the aikinite-bismuthinite series. In plane-polarized light, the new species is brownish grey with no perceptible pleochroism; under crossed nicols in oil immersion, it presents a weak anisotropy with dark brown tints. Minimum and maximum reflectance values (in %) in air are: 40.7-42.15 (470 nm), 41.2-43.1 (546 nm), 41.2-43.35 (589 nm) and 40.7-43.3 (650 nm). Cleavage is perfect along 001 I and well developed on {010}. Abundant polysynthetic twinning is observed on (010). The mean micro-indentation hardness is 190 kg/mm(2) (Mohs hardness 3.3), and the calculated density is 6.58 g/cm(3). Electron-microprobe analyses yield (wt%; mean result of seven analyses): Cu 16.48, Pb 2.10, Fe 0.77, Bi 60.70, Sb 0.35, S 19.16, Se 0.04, total 99.60. The resulting empirical chemical formula is (Cu15.24Fe0.80Pb0.60)(Sigma 16.64)(Bi17.07Sb0.17)(Sigma 17.24)(S35.09Se0.03)(Sigma 35.12), in accordance with the formula derived from the single-crystal refinement of the structure, (Cu,Fe)Cu14PbBi17S35. Pizgrischite is monoclinic, space group C2/m, with the following unit-cell parameters: a 35.054(2), b3.91123(I), c43.192(2) angstrom, beta 96.713(4)degrees, V5881.24 angstrom(3), Z=4. The strongest seven X-ray powder-diffraction lines [d in angstrom (I)(hkl)] are: 5.364(40)((6) over bar 04), 4.080(50)((8) over bar 05), 3.120(40)(118), 3.104(68)((3) over bar 18), 2.759(53) ((9) over bar 11),2.752(44)(910) and 1.956(100)(020). The crystal structure is an expanded monoclinic derivative of kupcikite. Pizgrischite belongs to the cuprobismutite series of bismuth sulfosalts but, sensu stricto, it is not a homologue of cuprobismutite. At the type locality. pizarischite is the result of the Alpine metamorphism under greenschist-facies conditions of pre-Tertiary hydrothermal Cu-Bi mineralization.

Experimental calcium oxalate crystal production and dissolution by selected wood rot fungi.

Twenty-six species of white-rotting Agaricomycotina fungi (Basidiomycota) were screened for their ability to produce calcium-oxalate (CaOx) crystals in vitro. Most were able to produce CaOx crystals in malt agar medium in the absence of additional calcium. In the same medium enriched with Ca2+, all the species produced CaOx crystals (weddellite or whewellite). Hyphae of four species (Ganoderma lucidum, Polyporus ciliatus, Pycnoporus cinnabarinus, and Trametes versicolor) were found coated with crystals (weddellite/whewellite). The production of CaOx crystals during the growth phase was confirmed by an investigation of the production kinetics for six of the species considered in the initial screening (Pleurotus citrinopileatus, Pleurotus eryngii, Pleurotus ostreatus, P. cinnabarinus, Trametes suaveolens, and T. versicolor). However, the crystals produced during the growth phase disappeared from the medium over time in four of the six species (P. citrinopileatus, P. eryngii, P. cinnabarinus, and T. suaveolens). For P. cinnabarinus, the disappearance of the crystals was correlated with a decrease in the total oxalate concentration measured in the medium from 0.65 μg mm−2 (at the maximum accumulation rate) to 0.30 μg mm−2. The decrease in the CaOx concentration was correlated with a change in mycelia morphology. The oxalate dissolution capability of all the species was also tested in a medium containing calcium oxalate as the sole source of carbon (modified Schlegel medium). Three species (Agaricus blazei, Pleurotus tuberregium, and P. ciliatus) presented a dissolution halo around the growth zone. This study shows that CaOx crystal production is a widespread phenomenon in white-rot fungi, and that an excess of Ca2+ can enhance CaOx crystal production. In addition, it shows that some white-rot fungal species are capable of dissolving CaOx crystals after growth has ceased. These results highlight a diversity of responses around the production or dissolution of calcium oxalate in white-rot fungi and reveal an unexpected potential importance of fungi on the oxalate cycle in the environment.

Heparan sulfate 6-O-sulfotransferase 1, a gene involved in extracellular sugar modifications, is mutated in patients with idiopathic hypogonadotrophic hypogonadism.

Neuronal development is the result of a multitude of neural migrations, which require extensive cell-cell communication. These processes are modulated by extracellular matrix components, such as heparan sulfate (HS) polysaccharides. HS is molecularly complex as a result of nonrandom modifications of the sugar moieties, including sulfations in specific positions. We report here mutations in HS 6-O-sulfotransferase 1 (HS6ST1) in families with idiopathic hypogonadotropic hypogonadism (IHH). IHH manifests as incomplete or absent puberty and infertility as a result of defects in gonadotropin-releasing hormone neuron development or function. IHH-associated HS6ST1 mutations display reduced activity in vitro and in vivo, suggesting that HS6ST1 and the complex modifications of extracellular sugars are critical for normal development in humans. Genetic experiments in Caenorhabditis elegans reveal that HS cell-specifically regulates neural branching in vivo in concert with other IHH-associated genes, including kal-1, the FGF receptor, and FGF. These findings are consistent with a model in which KAL1 can act as a modulatory coligand with FGF to activate the FGF receptor in an HS-dependent manner.

A single mutation in enzyme I of the sugar phosphotransferase system confers penicillin tolerance to Streptococcus gordonii.

Tolerance is a poorly understood phenomenon that allows bacteria exposed to a bactericidal antibiotic to stop their growth and withstand drug-induced killing. This survival ability has been implicated in antibiotic treatment failures. Here, we describe a single nucleotide mutation (tol1) in a tolerant Streptococcus gordonii strain (Tol1) that is sufficient to provide tolerance in vitro and in vivo. It induces a proline-to-arginine substitution (P483R) in the homodimerization interface of enzyme I of the sugar phosphotransferase system, resulting in diminished sugar uptake. In vitro, the susceptible wild-type (WT) and Tol1 cultures lost 4.5 and 0.6 log(10) CFU/ml, respectively, after 24 h of penicillin exposure. The introduction of tol1 into the WT (WT P483R) conferred tolerance (a loss of 0.7 log(10) CFU/ml/24 h), whereas restitution of the parent sequence in Tol1 (Tol1 R483P) restored antibiotic susceptibility. Moreover, penicillin treatment of rats in an experimental model of endocarditis showed a complete inversion in the outcome, with a failure of therapy in rats infected with WT P483R and the complete disappearance of bacteria in animals infected with Tol1 R483P.

Sublingual sugar for hypoglycaemia in children with severe malaria: a pilot clinical study.

BACKGROUND: Hypoglycaemia is a poor prognostic indicator in severe malaria. Intravenous infusions are rarely feasible in rural areas. The efficacy of sublingual sugar (SLS) was assessed in a pilot randomized controlled trial among hypoglycaemic children with severe malaria in Mali. METHODS: Of 151 patients with presumed severe malaria, 23 children with blood glucose concentrations < 60 mg/dl (< 3.3 mmol/l) were assigned randomly to receive either intravenous 10% glucose (IVG; n = 9) or sublingual sugar (SLS; n = 14). In SLS, a teaspoon of sugar, moistened with a few drops of water, was gently placed under the tongue every 20 minutes. The child was put in the recovery position. Blood glucose concentration (BGC) was measured every 5-10 minutes for the first hour. All children were treated for malaria with intramuscular artemether. The primary outcome measure was treatment response, defined as reaching a BGC of >or= 3.3 mmol/l (60 mg/dl) within 40 minutes after admission. Secondary outcome measures were early treatment response at 20 minutes, relapse (early and late), maximal BGC gain (CGmax), and treatment delay. RESULTS: There was no significant difference between the groups in the primary outcome measure. Treatment response occurred in 71% and 67% for SLS and IVG, respectively. Among the responders, relapses occurred in 30% on SLS at 40 minutes and in 17% on IVG at 20 minutes. There was one fatality in each group. Treatment failures in the SLS group were related to children with clenched teeth or swallowing the sugar, whereas in the IVG group, they were due to unavoidable delays in beginning an infusion (median time 17.5 min (range 3-40).Among SLS, the BGC increase was rapid among the nine patients who really kept the sugar sublingually. All but one increased their BGC by 10 minutes with a mean gain of 44 mg/dl (95%CI: 20.5-63.4). CONCLUSION: Sublingual sugar appears to be a child-friendly, well-tolerated and effective promising method of raising blood glucose in severely ill children. More frequent repeated doses are needed to prevent relapse. Children should be monitored for early swallowing which leads to delayed absorption, and in this case another dose of sugar should be given. Sublingual sugar could be proposed as an immediate "first aid" measure while awaiting intravenous glucose. In many cases it may avert the need for intravenous glucose.

Crystal structure of NLRC4 reveals its autoinhibition mechanism.

Nucleotide-binding and oligomerization domain-like receptor (NLR) proteins oligomerize into multiprotein complexes termed inflammasomes when activated. Their autoinhibition mechanism remains poorly defined. Here, we report the crystal structure of mouse NLRC4 in a closed form. The adenosine diphosphate-mediated interaction between the central nucleotide-binding domain (NBD) and the winged-helix domain (WHD) was critical for stabilizing the closed conformation of NLRC4. The helical domain HD2 repressively contacted a conserved and functionally important α-helix of the NBD. The C-terminal leucine-rich repeat (LRR) domain is positioned to sterically occlude one side of the NBD domain and consequently sequester NLRC4 in a monomeric state. Disruption of ADP-mediated NBD-WHD or NBD-HD2/NBD-LRR interactions resulted in constitutive activation of NLRC4. Together, our data reveal the NBD-organized cooperative autoinhibition mechanism of NLRC4 and provide insight into its activation.

A missing sugar prevents glucose entry: a new twist on insulin secretion.

The signaling pathway that regulates glucose-stimulated insulin secretion depends on glucose metabolism, which is itself controlled by glucokinase. In a recent issue of Cell, show that altering N-glycosylation of the GLUT2 glucose transporter prevents its anchoring and retention at the cell surface; this impairs glucose uptake and insulin secretion.

Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps

Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Résumé grand public Comme toute matière, la roche est sensible à son environnement et cherche à s'adapter pour acquérir un état stable (état d'équilibre). Les changements des conditions physiques (température et pression) vont ainsi impliquer des modifications dans la roche. Le métamorphisme est l'étude de ces changements. Les minéraux qui constituent la roche peuvent modifier, leur structure, leur chimie ou être remplacer par d'autres minéraux plus stables. Il est ainsi crucial de déterminer les processus responsables et limitant de la croissance minérale. Trois processus permettent la croissance ; (1) la dissolution des éléments du réactant, (2) le transport de ces éléments vers le site de croissance, (3) l'incorporation de ces éléments dans la nouvelle structure. Cette thèse se focalise sur les structures des minéraux de haute pression (forme, zonation chimique, structure interne) pour essayer de déterminer les facteurs importants à l'origine de leur état final. Les zones d'étude se situent dans la zone de Sésia. La première partie traite de la problématique liée à l'incorporation d'un élément dans une structure minérale. A l'image de la croissance humaine, les irrégularités minéralogiques permettent de mettre en lumière un dysfonctionnement de la croissance due à un excès ou à une carence d'un élément. Bien dosé, cet élément est cependant essentiel à la croissance. Les zoisites (épidotes) des métabasites de la région de Cima di Bonze montrent une zonation chimique en sablier. Dans cette zonation la teneur en fer excède la capacité maximum que peut contenir la structure orthorhombique de la zoisite. Des défauts de structure permettent l'accommodation de cet excès. La zoisite peut ainsi adapter sa structure pour permettre l'incorporation d'une relativement grande quantité de fer. Les études précédentes montraient, pour des conditions similaires, la formation de deux épidotes distinctes. La deuxième partie se penche sur la compétition entre le minéral qui fait sa croissance et les minéraux (réactants) qui l'entourent. Les métapélites de la région du Monte Mucrone contiennent des grenats atollaires. Des études détaillées de la texture et de la zonation chimique du grenat ainsi qu'une modélisation thermodynamique ont permis de mieux cerner les facteurs importants responsables de la forme atollaire. Cette structure est obtenue par un changement du comportement de la croissance du grenat le long d'un chemin P-T hercynien. Dans un premier stade, le grenat croît rapidement et consume peu le quartz de la matrice. La croissance se fait ainsi le long des jointures des grains de quartz. Dans un second temps, les changements de conditions PT donnent une croissance lente du grenat et une forte consommation du quartz. Le grenat peut ainsi développer sa forme dodécaédrale classique. La troisième partie s'intéresse aux distances de transport par diffusion d'un élément (ici l'argon) durant la haute pression. Pour ce faire, un profile d'âges 40Ar/39Ar sur biotite a été mesuré depuis un veine de haute pression riche en argon jusque dans son encaissant (granitoïd du Monte Mucrone). Le profile montre une répartition des âges suivant une courbe de diffusion. Le transport se fait sur une longueur de deux centimètre avec l'aide d'un fluide. Il est réduit à une échelle millimétrique quand la phase fluide disparaît. Cette étude montre ainsi les difficultés de transport des éléments durant la haute pression ne permettant pas un rééquilibrage de la roche à grande échelle. Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Résumé de thèse Les processus de croissance (diffusion des éléments et les réactions d'interface) et les conditions dans lesquelles les minéraux grandissent (température, pression, fluide, composition chimique de la roche), déterminent la texture ainsi que la zonation des minéraux. Cette thèse se focalise, par le biais de textures peu communes, sur trois différents processus impliqués dans la croissance minérale à haute pression (Zone de Sésia, Alpes de l'Ouest, Italie). L'incorporation d'un élément dans une structure minérale ne peut se faire que dans des sites en accord avec la taille et la charge ionique de l'élément. De plus, la balance de charge doit être maintenue dans le minéral. La régularité de la structure cristalline fixe ainsi une limite maximum de concentration d'un élément donné. Les zoisites provenant des métabasites de la région de Cima di Bonze montrent des zonations en sablier caractérisées par une concentration anormale en fer. La zonation se marque par une différente teinte de biréfringence et par un plus grand angle d'extinction que le reste de la zoisite. Une inter-croissance de clinozoisite à l'intérieur de la structure orthorhombique de la zoisite peut ainsi être suspectée. Les analyses XRD (diffraction des rayons x) ainsi que les analyses Raman ne confirment pas cette suspicion. Seules les analyses TEM (microscope à électrons transmis) montrent des défauts de structure pouvant être interprétés comme des modules de clinozoisite. Ils ne peuvent cependant pas être considérés comme une phase thermodynamique. Un nouveau trou d'immiscibilité entre deux zoisite (X ep= 0.1 and Xep = 0.15) a ainsi pu être établi. Dans les métapélites la région du Monte Mucrone, des grenats fortement zonés montrent une évolution texturale singulière. Ils présentent une forme initiale de `champignon' qui se développe pour former une structure atollaire finale. L'étude conjuguée de la structure 3D et des zonations, ainsi que l'établissement d'un model thermodynamique, indiquent que ces structures proviennent de deux épisodes de croissances : (1) La croissance du grenat durant un chemin prograde hercynien (de 525 °C et 6.2 kbar à 640 °C et 9 kbar) permet la formation des textures atollaires. Elles sont le résultat d'une croissance poecilitique initiale suivie d'une croissance idiomorphique du grenat. (2) La structure est rendue plus complexe par la cristallisation d'un grenat homogène tout autour ainsi qu'à l'intérieur du grenat hercynien durant la haute pression alpine (550 °C and 20 kbar). L'arrivée de l'eau durant la haute pression facilite le transport d'éléments et permet une cristallisation rapide du grenat. La diffusion peut être un facteur limitant de la croissance minéralogique. Elle a aussi une grande importance pour la géochronologie. Une veine de haute pression à l'intérieur du granitoïde du Monte Mucrone a été étudiée dans le but de déterminer la distance de diffusion de l'argon. Le profile d'âges 40Ar/39Ar sur biotites, établi de la veine vers le métagranitoïde, suit une courbe de diffusion. Les âges sont élevés proche de la veine (800 Ma) puis décroissent jusqu'à des âges homogènes (170-150 Ma) à deux centimètres de la veine. La présence de fluide, marqué par de hautes concentrations en chlore, permet une diffusion centimétrique. Cependant, la distance est réduite à une échelle millimétrique quand le fluide est absent. Les très faibles distances de diffusion préservent les âges pré-alpins et impliquent un événement géologique pour les âges de 170-150 Ma. Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Thesis abstract Rock textures and zonings are the consequence of growth processes (element diffusion and interface reaction) steered by the environment in which they grew (pressure, differential stress, temperature, fluid and rock composition). The thesis presented here focuses on three different topics, each of it dealing with aspects of mineral growth processes during subduction, in a high-pressure environment. All studies were conducted in the Sesia Zone of the Western European Alps, Italy. The first study addresses the crystallography and geochemistry of element incorporation in zoisite, one of the major hydrous minerals found in subduction zone rocks. Elements can be incorporated into a mineral structure only on crystallographic sites that offer enough space for the ion and the overall charge balance has to be maintained. Element concentrations are hence limited. Incorporation of some elements produces complex zoning, including hourglass like patterns, which are the focus of the first contribution. Zoisites from Cima di Bonze (Sesia Zone) show spectacular hourglass zoning defined by Fe-content variations. The hourglass zones have a distinct birefringence and a different extinction angle than the regular part of the zoisite. We show by detailed XRD (X-ray diffraction) and confocal Raman analyses that the high Fe-zones are nevertheless zoisite, and not clinozoisite as one might expect. High resolution TEM (transmission electron microscopy) analyses show planar defects on (100) that can be interpreted as small-scale clinozoisite modules. However, these clinozoisites cannot be interpreted as a distinctive thermodynamic phase and the entire mineral has to be considered as zoisite. The miscibility gap between two zoisites (Xep = 0.1 and Xep = 0.15) can be then definite at 550 ± 50°C and 14 to 20 Kbar. Strongly zoned garnets in quartz rich metapelite from the Monte Mucrone area (Sesia Zone) show evolution form 3D mushroom to atoll structure. The second contribution presents textural investigations, garnet zoning and thermodynamic modeling that demonstrate that atoll garnets are the result of two distinctive growth events. (1) Garnet atoll structure is already formed during a prograde Hercynian path from 525 °C and 6.2 kbar to 640 °C and 9 kbar. It results in an initial poikilitic growth followed by a final idiomorphic growth event. (2) Alpine HP garnet are homogenous (550 °C and 20 kbar) and grew around and also inside the Hercynian garnet. Lack of prograde Alpine garnet and fast growth of the HP garnet is explained by the absence of water during much of the prograde path. Water saturation was only observed towards the end, close towards the peak metamorphic conditions. Diffusion could be a limiting factor for crystal growth. It has also a great importance in geochronology. HP vein inside the metagranitoide of the Monte Mucrone (~300 Ma) was investigated to determine argon diffusion scales during high-pressure metamorphism. 40Ar/39Ar biotite ages profile from the vein toward the metagranodiorite show a diffusion curve: old ages (800 Ma) located close to the vein decrease until homogenous 170-150 Ma ages are obtained, two centimeter away from the vein. Centimeter-scale diffusion occurs with help of a fluid phase marked by high chlorine concentrations. Argon diffusion is reduced to a millimeter scale when free fluid is absent. Very short diffusion distance permits to preserve pre-Alpine ages. The 170-150 Ma ages are considered to be geologic meaningful, probably resulting from the extensional tectonics linked to opening of the Tethian ocean.

Electron microscopy of RecA-DNA complexes: Two different states, their functional significance and relation to the solved crystal structure

Seven different electron microscopy techniques habe been employed to study the RecA protein of E. coli. This review provides a summary of the conclusions that have been drawn from these studies, and attempts to relate these observations to models for the role of RecA protein in homologous recombination.

The extended GLUT-family of sugar/polyol transport facilitators: nomenclature, sequence characteristics, and potential function of its novel members (review).

During the last 2 years, several novel genes that encode glucose transporter-like proteins have been identified and characterized. Because of their sequence similarity with GLUT1, these genes appear to belong to the family of solute carriers 2A (SLC2A, protein symbol GLUT). Sequence comparisons of all 13 family members allow the definition of characteristic sugar/polyol transporter signatures: (1) the presence of 12 membrane-spanning helices, (2) seven conserved glycine residues in the helices, (3) several basic and acidic residues at the intracellular surface of the proteins, (4) two conserved tryptophan residues, and (5) two conserved tyrosine residues. On the basis of sequence similarities and characteristic elements, the extended GLUT family can be divided into three subfamilies, namely class I (the previously known glucose transporters GLUT1-4), class II (the previously known fructose transporter GLUT5, the GLUT7, GLUT9 and GLUT11), and class III (GLUT6, 8, 10, 12, and the myo-inositol transporter HMIT1). Functional characteristics have been reported for some of the novel GLUTs. Like GLUT1-4, they exhibit a tissue/cell-specific expression (GLUT6, leukocytes, brain; GLUT8, testis, blastocysts, brain, muscle, adipocytes; GLUT9, liver, kidney; GLUT10, liver, pancreas; GLUT11, heart, skeletal muscle). GLUT6 and GLUT8 appear to be regulated by sub-cellular redistribution, because they are targeted to intra-cellular compartments by dileucine motifs in a dynamin dependent manner. Sugar transport has been reported for GLUT6, 8, and 11; HMIT1 has been shown to be a H+/myo-inositol co-transporter. Thus, the members of the extended GLUT family exhibit a surprisingly diverse substrate specificity, and the definition of sequence elements determining this substrate specificity will require a full functional characterization of all members.

Crystal packing modifies ligand binding affinity: the case of aldose reductase.

The relationship between the structures of protein-ligand complexes existing in the crystal and in solution, essential in the case of fragment-based screening by X-ray crystallography (FBS-X), has been often an object of controversy. To address this question, simultaneous co-crystallization and soaking of two inhibitors with different ratios, Fidarestat (FID; K(d) = 6.5 nM) and IDD594 (594; K(d) = 61 nM), which bind to h-aldose reductase (AR), have been performed. The subatomic resolution of the crystal structures allows the differentiation of both inhibitors, even when the structures are almost superposed. We have determined the occupation ratio in solution by mass spectrometry (MS) Occ(FID)/Occ(594) = 2.7 and by X-ray crystallography Occ(FID)/Occ(594) = 0.6. The occupancies in the crystal and in solution differ 4.6 times, implying that ligand binding potency is influenced by crystal contacts. A structural analysis shows that the Loop A (residues 122-130), which is exposed to the solvent, is flexible in solution, and is involved in packing contacts within the crystal. Furthermore, inhibitor 594 contacts the base of Loop A, stabilizing it, while inhibitor FID does not. This is shown by the difference in B-factors of the Loop A between the AR-594 and AR-FID complexes. A stable loop diminishes the entropic energy barrier to binding, favoring 594 versus FID. Therefore, the effect of the crystal environment should be taken into consideration in the X-ray diffraction analysis of ligand binding to proteins. This conclusion highlights the need for additional methodologies in the case of FBS-X to validate this powerful screening technique, which is widely used.

Quantitative analysis of crystal/grain sizes and their distributions in 2D and 3D

We review methods to estimate the average crystal (grain) size and the crystal (grain) size distribution in solid rocks. Average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock's microstructure. The primary data for grain size data are either 1D (i.e. line intercept methods), 2D (area analysis) or 3D (e.g., computed tomography, serial sectioning). These data have been used for different data treatments over the years, whereas several studies assume a certain probability function (e.g., logarithm, square root) to calculate statistical parameters as the mean, median, mode or the skewness of a crystal size distribution. The finally calculated average grain sizes have to be compatible between the different grain size estimation approaches in order to be properly applied, for example, in paleo-piezometers or grain size sensitive flow laws. Such compatibility is tested for different data treatments using one- and two-dimensional measurements. We propose an empirical conversion matrix for different datasets. These conversion factors provide the option to make different datasets compatible with each other, although the primary calculations were obtained in different ways. In order to present an average grain size, we propose to use the area-weighted and volume-weighted mean in the case of unimodal grain size distributions, respectively, for 2D and 3D measurements. The shape of the crystal size distribution is important for studies of nucleation and growth of minerals. The shape of the crystal size distribution of garnet populations is compared between different 2D and 3D measurements, which are serial sectioning and computed tomography. The comparison of different direct measured 3D data; stereological data and direct presented 20 data show the problems of the quality of the smallest grain sizes and the overestimation of small grain sizes in stereological tools, depending on the type of CSD. (C) 2011 Published by Elsevier Ltd.

Crystal structure of yeast peroxisomal multifunctional enzyme: structural basis for substrate specificity of (3R)-hydroxyacyl-CoA dehydrogenase units.

(3R)-hydroxyacyl-CoA dehydrogenase is part of multifunctional enzyme type 2 (MFE-2) of peroxisomal fatty acid beta-oxidation. The MFE-2 protein from yeasts contains in the same polypeptide chain two dehydrogenases (A and B), which possess difference in substrate specificity. The crystal structure of Candida tropicalis (3R)-hydroxyacyl-CoA dehydrogenase AB heterodimer, consisting of dehydrogenase A and B, determined at the resolution of 2.2A, shows overall similarity with the prototypic counterpart from rat, but also important differences that explain the substrate specificity differences observed. Docking studies suggest that dehydrogenase A binds the hydrophobic fatty acyl chain of a medium-chain-length ((3R)-OH-C10) substrate as bent into the binding pocket, whereas the short-chain substrates are dislocated by two mechanisms: (i) a short-chain-length 3-hydroxyacyl group ((3R)-OH-C4) does not reach the hydrophobic contacts needed for anchoring the substrate into the active site; and (ii) Leu44 in the loop above the NAD(+) cofactor attracts short-chain-length substrates away from the active site. Dehydrogenase B, which can use a (3R)-OH-C4 substrate, has a more shallow binding pocket and the substrate is correctly placed for catalysis. Based on the current structure, and together with the structure of the 2-enoyl-CoA hydratase 2 unit of yeast MFE-2 it becomes obvious that in yeast and mammalian MFE-2s, despite basically identical functional domains, the assembly of these domains into a mature, dimeric multifunctional enzyme is very different.